Rehman, Abida R (2000) Morphology of the fallopian tube during the ovarian cycle. (MPhil thesis), Kingston University, .

Abstract

In the reproductive life of the non-pregnant female, the Fallopian tube functions to nourish and transport the ovum towards the uterus in a precisely timed manner. These processes are facilitated by cyclical changes in the mucosa and musculature layers of the Fallopian tube during the ovarian cycle. The volume of tubal fluid in the Fallopian tube also varies during the ovarian cycle. However, there is very little information on any morphological changes in the tubal vasculature which may be associated with the above mentioned variations in the tubal structure and function during the ovarian cycle. The aim of the present study was to investigate the morphology of tubal blood and lymph vessels in the different layers of the isthmus, ampulla and infundibulum, and to determine whether there were any cyclical changes occurring in the mucosa at the: (A) early/mid proliferative phase (B) late proliferative/ovulatory/early luteal phase and (C) mid/late luteal phase. For this purpose, the serosal, muscle and mucosal layers of the isthmus, ampulla and infundibulum were studied by light microscopy. In order to identify any possible cyclical changes in vascularity of the isthmus, ampulla and infundibulum, mucosal blood capillaries were counted in toluidine blue stained sections. Distinction between blood and lymph vessels was achieved using a blood vascular endothelial marker, CD34. Furthermore, any possible cyclical alterations in the fine structure of ampullary mucosal blood capillaries were examined by transmission electron microscopy. The serosal layer consisted of large arterioles and veins. In the muscle layer, when detected, small blood vessels were present. Mucosa consisted of two types of folds, branched and unbranched. Both types were present in the ampulla and infundibulum (fimbriae), whereas the isthmus consisted mainly of shorter and thicker unbranched folds. Arrangement of the different types of blood vessels was different in these two types of mucosal folds. Branched folds in the ampulla and infundibulum (fimbriae) contained arterioles, blood capillaries and venules. Arterioles were confined to the core and base of the folds, whereas blood capillaries and venules were distributed in all parts of these folds. Unbranched folds from the ampulla and infundibulum contained blood capillaries and venules. Isthmic unbranched folds contained only blood capillaries. The epithelial cells/blood capillary ratio was lowest in all three groups of the infundibulum compared with the ampulla and isthmus, the lowest being in Group A (4 epithelial cells/blood capillary). However, in Group A, the isthmus had the highest epithelial cells/blood capillary ratio (56 epithelial cells/blood capillary) compared to Group B and Group C in the three regions. These observations suggest that the isthmic mucosal folds may be least vascular and the infundibular (fimbrial) mucosal folds the most vascular prior to ovulation. Significant variations in the epithelial cells/blood capillary/fold ratio within each region and group (P<0.00 1), suggests that each mucosal fold may be functioning separately from another fold within that cross section of Fallopian tube. Immunohistochemical staining using CD34 gave variable results in different layers. All types of blood vessels were CD34 positive except for serosal and muscle arterioles which were mostly CD34 negative. In addition, mucosal stromal cells were CD34 positive in some folds within the same patient, suggesting the selective expression of CD34 in different folds. When detected, mucosal lymphatics had a central position in the folds in the three regions in both branched and unbranched folds. In branched folds, lymph capillaries were present not only in the central core but also in the side branches, suggesting a more extensive lymph vascular network in these folds. By transmission electron microscopy, ampullary mucosal blood capillaries were examined from the three groups of patients. An unexpected finding was the sparse number of ampullary subepithelial blood capillaries in both types of folds. Ultrastructural examination revealed morphological alterations in both continuous and fenestrated blood capillary wall. These modifications consisted of varying degrees in shape and thickness of the endothelial cytoplasm and nuclei and were observed in all three group of patients. Nuclei were thin and orientated circumferencially around the lumen, suggestive of blood capillary dilatation. In other blood capillaries, nuclei appeared to be thicker than the cytoplasm and bulged into the lumen. Pore- like structures were found only in fenestrated blood capillaries and were confined to the attentuated portion of the cytoplasm. The observations mentioned above, in the different regions of the Fallopian tubes, support the view that there are variations occurring in the blood vasculature and lymphatics in different folds in the three regions of the Fallopian tube during the ovarian cycle. Further studies are required to determine their physiological and clinical relevance.

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